1FSCK(8) System Administration FSCK(8)
2
6 fsck - check and repair a Linux filesystem
7
9 fsck [-lsAVRTMNP] [-r [fd]] [-C [fd]] [-t fstype] [filesystem...] [--]
10 [fs-specific-options]
11
13 fsck is used to check and optionally repair one or more Linux filesys‐
14 tems. filesys can be a device name (e.g., /dev/hdc1, /dev/sdb2), a
15 mount point (e.g., /, /usr, /home), or an filesystem label or UUID
16 specifier (e.g., UUID=8868abf6-88c5-4a83-98b8-bfc24057f7bd or
17 LABEL=root). Normally, the fsck program will try to handle filesystems
18 on different physical disk drives in parallel to reduce the total
19 amount of time needed to check all of them.
20 If no filesystems are specified on the command line, and the -A option
22 is not specified, fsck will default to checking filesystems in
23 /etc/fstab serially. This is equivalent to the -As options.
24 The exit status returned by fsck is the sum of the following condi‐
26 tions:
27 0 No errors
29 1 Filesystem errors corrected
30 2 System should be rebooted
31 4 Filesystem errors left uncorrected
32 8 Operational error
33 16 Usage or syntax error
34 32 Checking canceled by user request
35 128 Shared-library error
36 The exit status returned when multiple filesystems are checked is the
38 bit-wise OR of the exit statuses for each filesystem that is checked.
39 In actuality, fsck is simply a front-end for the various filesystem
41 checkers (fsck.fstype) available under Linux. The filesystem-specific
42 checker is searched for in the PATH environment variable. If the PATH
43 is undefined then fallback to "/sbin".
44 Please see the filesystem-specific checker manual pages for further
46 details.
47
49 -l Create an exclusive flock(2) lock file
50 (/run/fsck/<diskname>.lock) for whole-disk device. This option
51 can be used with one device only (this means that -A and -l are
52 mutually exclusive). This option is recommended when more
53 fsck(8) instances are executed in the same time. The option is
54 ignored when used for multiple devices or for non-rotating
55 disks. fsck does not lock underlying devices when executed to
56 check stacked devices (e.g. MD or DM) – this feature is not
57 implemented yet.
58 -r [fd]
60 Report certain statistics for each fsck when it completes.
61 These statistics include the exit status, the maximum run set
62 size (in kilobytes), the elapsed all-clock time and the user and
63 system CPU time used by the fsck run. For example:
64 /dev/sda1: status 0, rss 92828, real 4.002804, user 2.677592,
66 sys 0.86186
67 GUI front-ends may specify a file descriptor fd, in which case
69 the progress bar information will be sent to that file descrip‐
70 tor in a machine parsable format. For example:
71 /dev/sda1 0 92828 4.002804 2.677592 0.86186
73 -s Serialize fsck operations. This is a good idea if you are
75 checking multiple filesystems and the checkers are in an inter‐
76 active mode. (Note: e2fsck(8) runs in an interactive mode by
77 default. To make e2fsck(8) run in a non-interactive mode, you
78 must either specify the -p or -a option, if you wish for errors
79 to be corrected automatically, or the -n option if you do not.)
80 -t fslist
82 Specifies the type(s) of filesystem to be checked. When the -A
83 flag is specified, only filesystems that match fslist are
84 checked. The fslist parameter is a comma-separated list of
85 filesystems and options specifiers. All of the filesystems in
86 this comma-separated list may be prefixed by a negation operator
87 'no' or '!', which requests that only those filesystems not
88 listed in fslist will be checked. If none of the filesystems in
89 fslist is prefixed by a negation operator, then only those
90 listed filesystems will be checked.
91 Options specifiers may be included in the comma-separated
93 fslist. They must have the format opts=fs-option. If an
94 options specifier is present, then only filesystems which con‐
95 tain fs-option in their mount options field of /etc/fstab will
96 be checked. If the options specifier is prefixed by a negation
97 operator, then only those filesystems that do not have fs-option
98 in their mount options field of /etc/fstab will be checked.
99 For example, if opts=ro appears in fslist, then only filesystems
101 listed in /etc/fstab with the ro option will be checked.
102 For compatibility with Mandrake distributions whose boot scripts
104 depend upon an unauthorized UI change to the fsck program, if a
105 filesystem type of loop is found in fslist, it is treated as if
106 opts=loop were specified as an argument to the -t option.
107 Normally, the filesystem type is deduced by searching for
109 filesys in the /etc/fstab file and using the corresponding
110 entry. If the type cannot be deduced, and there is only a sin‐
111 gle filesystem given as an argument to the -t option, fsck will
112 use the specified filesystem type. If this type is not avail‐
113 able, then the default filesystem type (currently ext2) is used.
114 -A Walk through the /etc/fstab file and try to check all filesys‐
116 tems in one run. This option is typically used from the /etc/rc
117 system initialization file, instead of multiple commands for
118 checking a single filesystem.
119 The root filesystem will be checked first unless the -P option
121 is specified (see below). After that, filesystems will be
122 checked in the order specified by the fs_passno (the sixth)
123 field in the /etc/fstab file. Filesystems with a fs_passno
124 value of 0 are skipped and are not checked at all. Filesystems
125 with a fs_passno value of greater than zero will be checked in
126 order, with filesystems with the lowest fs_passno number being
127 checked first. If there are multiple filesystems with the same
128 pass number, fsck will attempt to check them in parallel,
129 although it will avoid running multiple filesystem checks on the
130 same physical disk.
131 fsck does not check stacked devices (RAIDs, dm-crypt, ...) in
133 parallel with any other device. See below for
134 FSCK_FORCE_ALL_PARALLEL setting. The /sys filesystem is used to
135 determine dependencies between devices.
136 Hence, a very common configuration in /etc/fstab files is to set
138 the root filesystem to have a fs_passno value of 1 and to set
139 all other filesystems to have a fs_passno value of 2. This will
140 allow fsck to automatically run filesystem checkers in parallel
141 if it is advantageous to do so. System administrators might
142 choose not to use this configuration if they need to avoid mul‐
143 tiple filesystem checks running in parallel for some reason –
144 for example, if the machine in question is short on memory so
145 that excessive paging is a concern.
146 fsck normally does not check whether the device actually exists
148 before calling a filesystem specific checker. Therefore non-
149 existing devices may cause the system to enter filesystem repair
150 mode during boot if the filesystem specific checker returns a
151 fatal error. The /etc/fstab mount option nofail may be used to
152 have fsck skip non-existing devices. fsck also skips non-exist‐
153 ing devices that have the special filesystem type auto.
154 -C [fd]
156 Display completion/progress bars for those filesystem checkers
157 (currently only for ext[234]) which support them. fsck will
158 manage the filesystem checkers so that only one of them will
159 display a progress bar at a time. GUI front-ends may specify a
160 file descriptor fd, in which case the progress bar information
161 will be sent to that file descriptor.
162 -M Do not check mounted filesystems and return an exit status of 0
164 for mounted filesystems.
165 -N Don't execute, just show what would be done.
167 -P When the -A flag is set, check the root filesystem in parallel
169 with the other filesystems. This is not the safest thing in the
170 world to do, since if the root filesystem is in doubt things
171 like the e2fsck(8) executable might be corrupted! This option
172 is mainly provided for those sysadmins who don't want to repar‐
173 tition the root filesystem to be small and compact (which is
174 really the right solution).
175 -R When checking all filesystems with the -A flag, skip the root
177 filesystem. (This is useful in case the root filesystem has
178 already been mounted read-write.)
179 -T Don't show the title on startup.
181 -V Produce verbose output, including all filesystem-specific com‐
183 mands that are executed.
184 -?, --help
186 Display help text and exit.
187 --version
189 Display version information and exit.
190
192 Options which are not understood by fsck are passed to the filesystem-
193 specific checker!
194 These options must not take arguments, as there is no way for fsck to
196 be able to properly guess which options take arguments and which don't.
197 Options and arguments which follow the -- are treated as filesystem-
199 specific options to be passed to the filesystem-specific checker.
200 Please note that fsck is not designed to pass arbitrarily complicated
202 options to filesystem-specific checkers. If you're doing something
203 complicated, please just execute the filesystem-specific checker
204 directly. If you pass fsck some horribly complicated options and argu‐
205 ments, and it doesn't do what you expect, don't bother reporting it as
206 a bug. You're almost certainly doing something that you shouldn't be
207 doing with fsck. Options to different filesystem-specific fsck's are
208 not standardized.
209
211 The fsck program's behavior is affected by the following environment
212 variables:
213 FSCK_FORCE_ALL_PARALLEL
215 If this environment variable is set, fsck will attempt to check
216 all of the specified filesystems in parallel, regardless of
217 whether the filesystems appear to be on the same device. (This
218 is useful for RAID systems or high-end storage systems such as
219 those sold by companies such as IBM or EMC.) Note that the
220 fs_passno value is still used.
221 FSCK_MAX_INST
223 This environment variable will limit the maximum number of
224 filesystem checkers that can be running at one time. This
225 allows configurations which have a large number of disks to
226 avoid fsck starting too many filesystem checkers at once, which
227 might overload CPU and memory resources available on the system.
228 If this value is zero, then an unlimited number of processes can
229 be spawned. This is currently the default, but future versions
230 of fsck may attempt to automatically determine how many filesys‐
231 tem checks can be run based on gathering accounting data from
232 the operating system.
233 PATH The PATH environment variable is used to find filesystem check‐
235 ers.
236 FSTAB_FILE
238 This environment variable allows the system administrator to
239 override the standard location of the /etc/fstab file. It is
240 also useful for developers who are testing fsck.
241 LIBBLKID_DEBUG=all
243 enables libblkid debug output.
244 LIBMOUNT_DEBUG=all
246 enables libmount debug output.
247
249 /etc/fstab
250
252 Theodore Ts'o <tytso@mit.edu>
253 Karel Zak <kzak@redhat.com>
254
256 fstab(5), mkfs(8), fsck.ext2(8) or fsck.ext3(8) or e2fsck(8),
257 fsck.cramfs(8), fsck.jfs(8), fsck.nfs(8), fsck.minix(8), fsck.msdos(8),
258 fsck.vfat(8), fsck.xfs(8), reiserfsck(8)
259
261 The fsck command is part of the util-linux package and is available
262 from Linux Kernel Archive ⟨https://www.kernel.org/pub/linux/utils/util-
263 linux/⟩.
264util-linux February 2009 FSCK(8)